1. Field of the Invention
This invention relates to nitrogen-free rinse cycle fabric softeners and more particularly to said softeners in the form of microemulsions which upon dilution with water release hydrophobic materials. These hydrophobic materials can be long chain oxygenated hydrocarbons, such as long chain esters, polyols and the like.
2. Description of Related Art
Fabric softening compositions and articles have long been employed to make washed laundry items softer to the touch and more comfortable to the wearer. Such compositions include solutions, emulsions, and particulate and powder products. Fabric softening articles include paper strips that have been impregnated with fabric softening compositions. Until recently, most of the commercially available rinse cycle fabric softeners were based on quaternary ammonium salts referred to broadly as Quats. These Quats are very hydrophobic, cationic surface-active agents. A commonly used example is dimethyl ditallowyl ammonium chloride. Now however these Quats are being banned from use because of ever increasing environmental restrictions.
Emulsions of fabric softening agents have been added to the rinse water of washing machines to soften laundry articles. Alternatively, such agents have been added to the wash water together with a detergent composition or the detergent composition can include a softening component to provide a "softergent". Fabric softening components, such as Quats, provide softening to fabric sheets in an automatic laundry dryer during tumbling in a heated environment.
The Quats may be represented by the formula: ##STR1## wherein R, R', R", and R'" are all alkyl groups, with at least one such alkyl groups being a higher alkyl having at least about eight carbon atoms and with the rest being lower alkyls having one or two carbon atoms, and with X.sup.- being a salt forming anion. The preferred Quats have been quaternary ammonium salts of di-lower alkyl and di-higher alkyl ammonium halides although mono-lower and tri-higher alkyl ammonium halides have also been used.
In addition to contributing to environmental problems, the Quats have other undesirable properties that militate against their use. For example, being cationic, they tend to react with anionic materials and thereby negate their intended fabric softening function. Moreover, they are not as readily biodegradable as is desirable. They also have been found to be toxic to aquatic organisms leading to harmful effects on aquatic life in lakes, rivers and other into which waste waters carrying such compounds might be emptied.
In past efforts to find replacements for quaternary ammonium salts as fabric softeners, such candidates as neoalkanamides, glyceryl esters, silicones, cationic-anionic complexes, bentonite and various lubricants have been suggested alone or in conjunction with quaternary ammonium salts. These measures have not been satisfactory because of a diminution of the softening effects or because they introduced other undesirable properties to the softening compositions.
In order to be efficient, a softening composition must fulfill at least two conditions. These compositions must:
(1) exhibit physical and chemical stability during storage in warehouses and on store shelves. Physical stability is defined herein to mean that no phase separation can occur.
(2) release the active softening ingredients, during the laundry rinse cycle, so that they deposit on the laundered fibers within a reasonable time.
Several attempts have previously been made to meet these conditions and to solve the drawbacks of the known fabric softening systems.
U.S. Pat. No. 3,928,212 describes softening agents which are polyhydric alcohol esters.
U.S. Pat. No. 4,126,562 mentions erythritol and pentaerythritol which may be reacted with higher fatty acids to produce fabric softeners.
It is therefore an object of this invention to provide rinse cycle fabric softeners that are nitrogen free.
It is another object to provide such nitrogen-free softeners in a physical form that renders them physically and chemically stable.
It is a further object that such softeners upon dilution with water become quickly available for deposition on fiber surfaces.
Still another object is to provide nitrogen-free softeners that meet environmental standards including biodegradability.
Other objects will become apparent to those skilled in the art upon a further reading of the specification.